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SYPS: Plasmen in ungewöhnlichen Situationen
SYPS 1: Symposium: Plasmas in unusual situations, Part I: Ultracold plasmas
SYPS 1.4: Hauptvortrag
Montag, 7. März 2005, 12:00–12:30, HU Audimax
Recent experiments with laser-cooled ion plasmas in a Penning trap — •M.J. Jensen1, J.J. Bollinger1, T. Hasegawa2, and D.H.E. Dubin3 — 1NIST, Boulder, CO 80305, USA — 2Univ. of Hyogo, Hyogo 678-1297, Japan — 3UCSD, La Jolla, CA 92093, USA
Up to ∼106 9Be+ ions are trapped in a 4.5 Tesla Penning trap and laser-cooled to ∼1 mK where the ions form a crystal with an interparticle spacing of ∼20 µm. This system is a realization of a strongly coupled one-component plasma. Through Bragg scattering and direct imaging we have observed 3-dimensional periodic crystals in this plasma. Recently, we have measured the temperature of the plasma when not laser-cooled. A slow heating rate of <100 mK/s, observed for the first 100-200 ms after turning off the laser-cooling, is followed by a sudden, rapid heating to 1-2 K in 100 ms as the plasma undergoes the solid-liquid phase transition at T=10 mK (Γ∼170). We will present evidence that this rapid heating is due to a sudden release of energy from weakly cooled degrees of freedom involving the cyclotron motion of trapped impurity ions. A method to suppress this rapid heating will be presented, and the prospects for observing the latent heat associated with the phase transition will be discussed.